Method for preparing monomer composition for synthesizing recycled plastic, apparatus for preparing monomer composition for synthesizing recycled plastic, and monomer composition for synthesizing recycled plastic, recycled plastic, and molded article using same

Abstract

The present invention relates to a method for preparing a monomer composition for synthesizing recycled plastic, to an apparatus for manufacturing a monomer composition for synthesizing recycled plastic, and to a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded article using same, the method comprising the steps of: depolymerizing a polycarbonate resin in alcohol; monitoring a Raman spectrum by alcohol or an aromatic diol compound obtained from the depolymerization reaction in a reactor in which the depolymerization reaction is progressed; and recovering the aromatic diol compound.

Description

Method for producing a monomer composition for synthesizing recycled plastic, apparatus for producing a monomer composition for synthesizing recycled plastic, and monomer composition for synthesizing recycled plastic, recycled plastic, and molded article using the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0109847, filed August 22, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for producing a monomer composition for synthesizing recycled plastic, which improves efficiency by optimizing reaction conditions through real-time monitoring of a process for recycling an aromatic diol compound by chemical decomposition of a polycarbonate resin, an apparatus for producing a monomer composition for synthesizing recycled plastic, and a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded article using the same.

[0004] Polycarbonate is a thermoplastic polymer with excellent properties such as excellent transparency, flexibility, and relatively low manufacturing cost.

[0005] Although polycarbonate is widely used for various purposes, concerns about the environment and health when it is disposed of have been continuously raised.

[0006] Currently, physical recycling methods are being implemented, but this method is accompanied by quality degradation, so research is being conducted on chemical recycling of polycarbonate.

[0007] Chemical decomposition of polycarbonate refers to obtaining a monomeric aromatic diol compound (e.g., bisphenol A (BPA)) through decomposition of polycarbonate, and then using this again for polymerization to obtain high-purity polycarbonate.

[0008] Representative examples of chemical decomposition include thermal decomposition, hydrolysis, and alcohol decomposition. Among these, the most common method is alcohol decomposition using a base catalyst. However, methanol decomposition has the drawback of using methanol, which is harmful to the human body. Ethanol decomposition also requires high temperature and high pressure conditions, resulting in low yields.

[0009] In addition, although a method for decomposing alcohol using an organic catalyst is known, it has disadvantages in terms of economic aspect.

[0010] Meanwhile, as the reaction scale in the polycarbonate decomposition reaction increases to tens of liters, the need to explore factors that indicate differences in the depolymerization tendency from the laboratory scale has arisen.

[0011] Previously, the conversion rate for the final product was analyzed using HPLC or NMR analysis, or samples were collected and analyzed during the reaction.

[0012] However, as the reaction scale increased, differences arose in the conversion rate of polycarbonate compared to the reaction conducted at the laboratory level, and in the timing and extent of formation of by-products.

[0013] The present invention provides a method for producing a monomer composition for synthesizing recycled plastic, or an apparatus for producing a monomer composition for synthesizing recycled plastic, which improves efficiency by optimizing reaction conditions through real-time monitoring of a process for recycling an aromatic diol compound by chemical decomposition of a polycarbonate resin.

[0014] In addition, the present invention provides a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded product using the method for producing the monomer composition for synthesizing recycled plastic or the apparatus for producing the monomer composition for synthesizing recycled plastic.

[0015] In order to solve the above problem, the present specification provides a method for producing a monomer composition for synthesizing recycled plastic, comprising the steps of: depolymerizing a polycarbonate resin in the presence of alcohol; monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained in the depolymerization reaction within a reactor in which the depolymerization reaction is performed; and recovering the aromatic diol compound.

[0016] The present specification also provides an apparatus for manufacturing a monomer composition for synthesizing recycled plastic, comprising: a reactor for depolymerizing a polycarbonate resin in the presence of alcohol; an inline analyzer inserted into the reactor for monitoring a Raman spectrum of an aromatic diol compound obtained in the depolymerization reaction or alcohol; and a recovery unit for recovering an aromatic diol compound obtained in the depolymerization reaction.

[0017] The present specification also provides a monomer composition for synthesizing recycled plastic, comprising an aromatic diol compound obtained by a method for producing the monomer composition for synthesizing recycled plastic or an apparatus for producing the monomer composition for synthesizing recycled plastic.

[0018] The present specification also provides a recycled plastic comprising a monomer composition for synthesizing the recycled plastic and a reaction product of a comonomer.

[0019] The present specification also provides a molded article comprising the recycled plastic.

[0020] Hereinafter, a method for producing a monomer composition for synthesizing recycled plastic according to a specific embodiment of the invention, an apparatus for producing a monomer composition for synthesizing recycled plastic, and a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded product using the same will be described in more detail.

[0021]

[0022] Unless explicitly stated otherwise in this specification, terminology is used only to describe specific embodiments and is not intended to limit the invention.

[0023] As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise.

[0024] The term "pH" used herein refers to the hydrogen ion concentration (pH), a numerical value indicating the degree of acidity or alkalinity of a substance. It is calculated by taking the reciprocal logarithm of the hydrogen ion dissociation concentration, and is used as a measure of the acidity and alkalinity of a substance.

[0025] As used herein, the term “including” means specifying a particular characteristic, region, integer, step, operation, element and / or component, but does not exclude the presence or addition of other particular characteristics, regions, integers, steps, operations, elements, components and / or groups.

[0026] In addition, terms including ordinal numbers, such as "first" and "second," in this specification are used to distinguish one component from another and are not limited by the ordinal numbers. For example, within the scope of the present invention, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

[0027]

[0028] 1. Method for producing a monomer composition for synthesizing recycled plastic

[0029] According to one embodiment of the invention, a method for producing a monomer composition for synthesizing recycled plastic may be provided, comprising the steps of: depolymerizing a polycarbonate resin in the presence of alcohol; monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained in the depolymerization reaction within a reactor in which the depolymerization reaction is performed; and recovering the aromatic diol compound.

[0030] The present inventors have experimentally confirmed that, in the process of recycling a polycarbonate resin by chemical decomposition, as in the method for producing a monomer composition for synthesizing recycled plastic of the above embodiment, by monitoring the Raman spectrum of an aromatic diol compound or alcohol obtained in the depolymerization reaction in a reactor in which the depolymerization reaction is carried out, the depolymerization reaction can be terminated at an optimal point, thereby recovering a high-purity aromatic diol compound in a high yield, and have completed the invention.

[0031] In particular, in the past, there was a limitation in finding the optimal reaction end point to secure the aromatic diol compound, which is the target material for recovery, in high purity and high yield by analyzing the conversion rate for the final product through HPLC or NMR analysis or by collecting and analyzing a sample at an arbitrary point during the reaction.

[0032] On the other hand, in the present invention, in the process of recycling polycarbonate resin by chemical decomposition, the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction is secured in real time while the depolymerization reaction is in progress through an analysis device installed in the reactor in which the depolymerization reaction is in progress, and by analyzing this, the approximate aromatic diol compound or alcohol can be obtained, so that the optimal reaction end point can be found more accurately, and by monitoring in real time whether or not reaction by-products are generated and minimizing by-products, it is possible to implement the effect of enabling the recovery of high-purity, high-yield aromatic diol compounds.

[0033] Specifically, the method for producing a monomer composition for synthesizing recycled plastic of the above embodiment may include a step of depolymerizing a polycarbonate resin in the presence of alcohol.

[0034] The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization or copolymerization reaction of a monomer including an aromatic diol compound and a carbonate precursor. When it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor, a homopolymer can be synthesized. In addition, when one type of aromatic diol compound and two or more types of carbonate precursors are used as the monomer, or two or more types of aromatic diol compounds and one type of carbonate precursor are used, or one or more types of other diols are used in addition to one type of aromatic diol compound and one type of carbonate precursor, and two or more types of carbonates are contained, a copolymer can be synthesized. The above homopolymer or copolymer may include all low-molecular-weight compounds, oligomers, and polymers according to the molecular weight range.

[0035] The above polycarbonate resin can be applied to various forms and types, including new polycarbonate resin produced through synthesis, recycled polycarbonate resin produced through a recycling process, or polycarbonate resin waste.

[0036] However, if necessary, before performing a depolymerization reaction of the polycarbonate resin, a pretreatment process of the polycarbonate resin may be performed to increase the efficiency of the process of recovering an aromatic diol compound and a carbonate precursor from the polycarbonate resin. Examples of the pretreatment process include washing, drying, grinding, glycol decomposition, etc., and the specific method of each pretreatment process is not limited, and various methods widely used in the process of recovering an aromatic diol compound and a carbonate precursor by depolymerization of a polycarbonate resin can be applied without limitation.

[0037] When the polycarbonate resin is depolymerized, the depolymerization reaction can be carried out under acidic, neutral, or alkaline conditions, and in particular, the depolymerization reaction can proceed under alkaline (alkaline) conditions. The type of the base is not particularly limited, and examples thereof include sodium hydroxide (NaOH) or potassium hydroxide (KOH). The base is a base catalyst that acts as a catalyst, and has the advantage of being economical compared to organic catalysts that are mainly used under mild conditions. More specifically, when the polycarbonate resin is depolymerized, the depolymerization reaction can proceed within a pH range of more than 8 and less than 12.

[0038] In the depolymerization reaction of the polycarbonate resin, the base may be reacted in an amount of 0.5 mol or less, or 0.4 mol or less, or 0.3 mol or less, or 0.1 mol or more, or 0.2 mol or more, or 0.1 to 0.5 mol, or 0.1 to 0.4 mol, or 0.1 to 0.3 mol, or 0.2 to 0.5 mol, or 0.2 to 0.4 mol, or 0.2 to 0.3 mol, per 1 mol of the polycarbonate resin. In the depolymerization reaction of the polycarbonate resin, if the base is reacted in an amount exceeding 0.5 mol per 1 mol of the polycarbonate resin, the amount of impurities increases due to the increased generation of alkali salts, which reduces the purity of the target recovered material and has a limitation in that the economic feasibility of the catalytic reaction decreases.

[0039] In addition, the depolymerization reaction of the polycarbonate resin can be carried out in the presence of alcohol. The present invention has the advantage of being able to stably obtain bisphenol A, a high-purity monomer, by decomposing the polycarbonate resin with alcohol, and additionally obtain a carbonate compound, such as a dialkyl carbonate, which has high added value as a reaction byproduct.

[0040] The number of hydroxyl groups in the above alcohol is not particularly limited, but may include, for example, monohydric alcohols. The monohydric alcohols are compounds having one hydroxyl group in the molecule.

[0041] In addition, the type of monovalent organic functional group bonded to the hydroxyl group in the monovalent alcohol is not particularly limited, but may include an organic functional group having 1 to 10 carbon atoms, or 1 to 6 carbon atoms, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or a combination of two or more thereof.

[0042] The alcohol may be a single compound or a mixture of two or more compounds. Specific examples of the alcohol are not particularly limited, but include, for example, ethanol, methanol, phenol, or mixtures thereof.

[0043] The content of the alcohol may be 5 to 15 moles, or 8 to 13 moles, per 1 mole of the polycarbonate resin. Since the alcohol has good solubility in bisphenol A, the alcohol within the above range must be included. If the content of the alcohol is excessively reduced to less than 5 moles per 1 mole of the polycarbonate resin, it is difficult for the alcohol decomposition of the polycarbonate resin to proceed sufficiently. On the other hand, if the content of the alcohol is excessively increased to more than 15 moles per 1 mole of the polycarbonate resin, the economic feasibility of the process may decrease due to excessive use of alcohol.

[0044] The solvent in which the depolymerization reaction of the above polycarbonate resin is carried out may include at least one organic solvent selected from the group consisting of tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate.

[0045] The organic solvent may include tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0046] More preferably, methylene chloride can be used as the organic solvent. When methylene chloride is used as the organic solvent, the solubility characteristics for polycarbonate are improved, which has the advantage of enhancing reactivity.

[0047] The content of the organic solvent may be 16 to 20 moles, or 16 to 18 moles, relative to 1 mole of the polycarbonate resin. In addition, the content of the organic solvent may be 1.5 to 2 moles relative to 1 mole of the alcohol. Within the above range, there is an advantage in that the polycarbonate resin, alcohol, and organic solvent are mixed, thereby allowing a depolymerization reaction of the polymer to proceed at a required level.

[0048] Meanwhile, the temperature at which the depolymerization reaction of the polycarbonate resin is performed is not particularly limited, but may be performed at, for example, 20°C to 100°C, or 50°C to 70°C. In addition, the time at which the depolymerization reaction of the polycarbonate resin is performed may be 1 hour to 30 hours, or 4 hours to 6 hours.

[0049] Specifically, the above conditions are mild process conditions compared to the existing pressurized / high-temperature process, and by performing stirring under the above conditions, the process can be performed in a mild process compared to the pressurized / high-temperature process, and in particular, there is an advantage in that the most efficient results can be obtained in terms of reproducibility and recognizability when stirring for 4 to 6 hours at 50 to 70 °C.

[0050] That is, the present invention has the advantage of being able to obtain a high-purity aromatic diol compound (e.g., bisphenol A) under mild conditions without using a pressurized / high-temperature process by controlling the type and amount of mixed solvent and the type and content of a base catalyst even without using an organic catalyst, and of being able to obtain diethyl carbonate as a byproduct by using ethanol.

[0051] Meanwhile, during the depolymerization reaction of the polycarbonate resin, an antioxidant may be added to the reaction solution. By adding the antioxidant, the aromatic diol compound recovered through recycling by chemical decomposition of the polycarbonate resin can satisfy a low color coordinate b* value equivalent to that of a commercially available reagent or reagent used for PC polymerization.

[0052] Specific examples of the above antioxidants are not particularly limited, and various antioxidants that have been widely used in the prior art can be applied without limitation. However, examples thereof include sodium hyposulfite, sodium sulfite, erythorbic acid, dibutylhydroxytoluene, butylhydroxyanisole, α-tocopherol, tocopherol acetate, L-ascorbic acid and its salts, L-ascorbic acid palmitate, L-ascorbic acid stearate, triamyl gallate, propyl gallate, or disodium ethylenediaminetetraacetate (EDTA), sodium pyrophosphate, sodium metaphosphate, or mixtures of two or more thereof.

[0053] The specific amount of the antioxidant to be added is not particularly limited, but for example, it may be added in a range of 0.1 wt% to 5 wt%, or 0.1 wt% to 1 wt%, based on the total weight of the reaction solution, at a level that does not affect the properties of the monomer composition for synthesizing recycled plastic.

[0054] Additionally, when the polycarbonate resin is depolymerized, the depolymerization reaction can be performed under a nitrogen atmosphere.

[0055] More specifically, the step of depolymerizing the polycarbonate resin may include a first step of dissolving the carbonate resin in an organic solvent; and a second step of adding and stirring a catalyst solution containing alcohol, a base, and an antioxidant. In the first and second steps, the contents of the alcohol, the organic solvent, the base, the antioxidant, and the polycarbonate resin are the same as those described above.

[0056] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the above embodiment may include a step of monitoring a Raman spectrum of an aromatic diol compound or alcohol obtained in the depolymerization reaction in a reactor in which the depolymerization reaction is performed. By monitoring the Raman spectrum of an aromatic diol compound or alcohol obtained in the depolymerization reaction in real time while the depolymerization reaction is in progress through an analysis device installed in the reactor in which the depolymerization reaction is performed, the optimal reaction end point can be more accurately found, and in addition, by monitoring in real time whether a reaction by-product is generated, by minimizing the by-product, it is possible to recover a high-purity, high-yield aromatic diol compound.

[0057] In the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction within the reactor where the depolymerization reaction is taking place, the Raman spectrum is data obtained through Raman analysis. The specific details of the Raman analysis method can be applied without limitation to various previously known analysis methods, analysis equipment, and analysis conditions. However, for example, the MarqMetrix All-in-one equipment can be utilized.

[0058] In particular, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction within the reactor in which the depolymerization reaction is carried out can be carried out using a Raman measuring device inserted within the reactor. More specifically, in the above embodiment, by utilizing an in-line probe, which is a Raman measuring device inserted within the reactor, it was possible to non-destructively analyze real-time chemical component changes within the solid / liquid reaction solution.

[0059] Accordingly, by observing in real time the Raman spectra of aromatic diol compounds (e.g., bisphenol A) generated through the depolymerization reaction of polycarbonate resins or alcohols (e.g., ethanol) participating in the reaction using in-line Raman analysis equipment, it was possible to indirectly predict how the concentration and content of aromatic diol compounds (or alcohols) change in real time. More specifically, a PLS (partial least squares) prediction model can be obtained through correlation between Raman spectrum data and the concentration and content values ​​obtained through HPLC analysis.

[0060] The Raman meter described above is manufactured to withstand the reaction pressure and is inserted into a reactor in which a depolymerization reaction is taking place, thereby allowing for real-time collection of reaction information. One end of the Raman meter can be brought into contact with the depolymerization reaction reactants, and the other end is connected to a computer, enabling real-time calculation and analysis of the acquired Raman spectrum. The specific details of the Raman meter described above can be applied without limitation to previously known techniques. However, as an example, BallProbe can be used.

[0061] As a specific example of monitoring the Raman spectrum, the step of monitoring the Raman spectrum by the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out may include the step of measuring the integral ratio of the aromatic diol compound according to the following mathematical formula 1.

[0062] [Mathematical Formula 1]

[0063] Aromatic diol compound integral ratio = {791.2 cm on Raman spectrum -1 861.5 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm-1 337.1 cm inland -1 (integral of the domain)}

[0064] In the above mathematical formula 1, 791.2 cm on the Raman spectrum -1 861.5 cm inland -1 The region is a spectrum due to aromatic diol compounds, and is located at 663.4 cm in the Raman spectrum. -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is the spectrum due to the reaction solvent.

[0065] In the above mathematical expression 1, the methylene chloride component used as the depolymerization reaction solvent does not participate in the depolymerization reaction, so the Raman band integral value of the reaction solvent was placed in the denominator as a standard value, and the aromatic diol compound Raman band integral value was taken in the numerator to calculate the relative integral value.

[0066] The aromatic diol compound integration ratio according to the above mathematical formula 1 has a value between 0 and 0.15, and starts from 0 to 0.06 at the beginning of the depolymerization reaction, rapidly increases to 0.1 or more, or 0.1 to 0.11, within 30 minutes after the start of the reaction, and tends to converge to a value between 0.11 and 0.15, or 0.11 and 0.13, or 0.110 and 0.125, or 0.115 and 0.125, or 0.115 and 0.122, or 0.12 and 0.122 after 30 minutes.

[0067] Through this tendency analysis, it was confirmed that when the aromatic diol compound integral ratio according to the above mathematical formula 1 is 0.115 to 0.125, or 0.115 to 0.122, or 0.12 to 0.122, terminating the depolymerization reaction ensures process efficiency while enabling recovery of high-purity, high-yield aromatic diol compounds. If the aromatic diol compound integral ratio according to the above mathematical formula 1 decreases to less than 0.115, it is difficult to sufficiently secure the yield of the aromatic diol compound. On the other hand, if the aromatic diol compound integral ratio according to the above mathematical formula 1 increases to more than 0.125, impurities other than the aromatic diol compound (e.g., impurities derived from the aromatic diol compound) increase, making it difficult to sufficiently secure the purity of the aromatic diol compound, and there is a limitation that the efficiency of the process decreases as the reaction proceeds for too long.

[0068] Meanwhile, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction within the reactor in which the depolymerization reaction is carried out may be repeatedly performed at intervals of 5 minutes or less. Specifically, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction within the reactor in which the depolymerization reaction is carried out may be repeatedly performed at intervals of 5 minutes or less, or 4 minutes or less, or 3 minutes or less while the depolymerization reaction is in progress. The shorter the interval for monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction, the more accurately the optimal reaction end point can be found, and the more the generation of reaction by-products can be minimized.

[0069] In addition, as another specific example of monitoring the Raman spectrum, the step of monitoring the Raman spectrum by the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out may include the step of measuring the alcohol integration ratio according to the following mathematical formula 2.

[0070] [Mathematical Formula 2]

[0071] Alcohol integral ratio = {849.7 cm on Raman spectrum -1 910 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)}

[0072] In the above mathematical equation 2, 849.7 cm on the Raman spectrum -1 910 cm inland -1 The region is a spectrum due to alcohol, and is 663.4 cm in the Raman spectrum. -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is the spectrum due to the reaction solvent.

[0073] In the above mathematical expression 2, the methylene chloride component used as the depolymerization reaction solvent does not participate in the depolymerization reaction, so the Raman band integral value of the reaction solvent was placed in the denominator as a standard value, and the alcohol Raman band integral value was taken in the numerator to calculate the relative integral value.

[0074] The alcohol integration ratio according to the above mathematical formula 2 has a value between 0 and 1.1, and starts from 0.15 or more, or 0.15 to 1.1 at the beginning of the depolymerization reaction, rapidly decreases to 0.11 or less, or 0.1 to 0.11 within 30 minutes after the start of the reaction, and tends to converge to a value between 0.09 and 0.1, or 0.095 to 0.1 after 30 minutes.

[0075] Through this tendency analysis, it was confirmed that when the alcohol integral ratio according to the above mathematical formula 2 is 0.09 to 0.1, or 0.095 to 0.1, terminating the depolymerization reaction ensures process efficiency while enabling recovery of high-purity, high-yield aromatic diol compounds. If the alcohol integral ratio according to the above mathematical formula 2 increases to exceed 0.1, it is difficult to sufficiently secure the yield of the aromatic diol compound. On the other hand, if the alcohol integral ratio according to the above mathematical formula 2 decreases to less than 0.09, impurities other than the aromatic diol compound (e.g., impurities derived from the aromatic diol compound) increase, making it difficult to sufficiently secure the purity of the aromatic diol compound, and there is a limitation that the efficiency of the process decreases as the reaction proceeds for too long.

[0076] In addition, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction within the reactor in which the depolymerization reaction is carried out may be repeatedly performed at intervals of 5 minutes or less. Specifically, the step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction within the reactor in which the depolymerization reaction is carried out may be repeatedly performed at intervals of 5 minutes or less, or 4 minutes or less, or 3 minutes or less while the depolymerization reaction is in progress. The shorter the interval for monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction, the more accurately the optimal reaction end point can be found, and the more the generation of reaction by-products can be minimized.

[0077] Meanwhile, the step of monitoring the Raman spectrum by the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out may further include the step of monitoring the Raman spectrum by impurities derived from the aromatic diol compound generated from the depolymerization reaction.

[0078] The above-mentioned aromatic diol compound-derived impurities are by-products generated as the depolymerization reaction proceeds excessively, and have the problem of lowering the purity of bisphenol A, which is the aromatic diol compound to be recovered. Therefore, by monitoring in real time the Raman spectrum due to the aromatic diol compound-derived impurities generated by the depolymerization reaction, the generation of reaction by-products can be monitored in real time, and by minimizing the by-products, it is possible to recover high-purity, high-yield aromatic diol compounds.

[0079] The above-mentioned aromatic diol compound-derived impurities refer to all substances other than the aromatic diol compound, which is the main recovery target substance of the present invention, and the specific type thereof is not particularly limited, but examples thereof include p-tert-butylphenol.

[0080] Specifically, the step of monitoring the Raman spectrum due to impurities derived from aromatic diol compounds generated by the above depolymerization reaction may include a step of measuring the integral ratio of impurities derived from aromatic diol compounds according to the following mathematical formula 3.

[0081] [Equation 3]

[0082] The integral ratio of impurities derived from aromatic diol compounds = {800 cm on the Raman spectrum -1 850 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)}

[0083] In the above mathematical formula 3, 800 cm on the Raman spectrum -1 850 cm inland -1 The region is a spectrum due to impurities derived from aromatic diol compounds, and is 663.4 cm in the Raman spectrum. -1 785.1 cm inland -1, and 234.8 cm -1 337.1 cm inland -1 The region is the spectrum due to the reaction solvent.

[0084] In the above mathematical expression 3, the methylene chloride component used as the depolymerization reaction solvent does not participate in the depolymerization reaction, so the Raman band integral value of the reaction solvent was placed in the denominator as a standard value, and the Raman band integral value of the impurity derived from the aromatic diol compound was taken in the numerator to calculate the relative integral value.

[0085] If the integral ratio of impurities derived from aromatic diol compounds according to the above mathematical formula 3 exceeds 0.12, terminating the depolymerization reaction ensures process efficiency while enabling recovery of high-purity, high-yield aromatic diol compounds. If the integral ratio of impurities derived from aromatic diol compounds according to the above mathematical formula 3 increases to exceed 0.12, impurities other than aromatic diol compounds (e.g., impurities derived from aromatic diol compounds) increase, making it difficult to sufficiently secure the purity of aromatic diol compounds, and there is a limitation that the efficiency of the process decreases as the reaction proceeds for too long.

[0086] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the above embodiment may include a step of recovering an aromatic diol compound obtained in the depolymerization reaction. Specific examples of the above aromatic diol compounds include bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, Examples thereof include 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, or a mixture of two or more thereof. Preferably, the aromatic diol compound of the monomer composition for synthesizing recycled plastic of the above embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0087] Specifically, the step of recovering the aromatic diol compound obtained in the depolymerization reaction may include a step of adding an acid so that the pH of the depolymerization reaction product becomes 2 to 8. The acid may be a strong acid, and examples thereof include hydrochloric acid (HCl).

[0088] In the step of adding acid so that the pH of the depolymerization product becomes 2 to 8, the salt of the aromatic diol compound contained in the depolymerization product can be converted into an aromatic diol compound. Since the depolymerization reaction proceeds under basic conditions, the produced aromatic diol compound exists in the form of a salt through a reaction with the base, thereby having hydrophilicity. Therefore, by adding acid, the salt of the aromatic diol compound contained in the depolymerization product can be converted into an aromatic diol compound, thereby inducing hydrophobicity.

[0089] Accordingly, in the step of removing impurities by adding water after the acid addition described below, layers can be formed that are divided into a water layer containing impurities and an organic solvent layer containing an aromatic diol compound and a carbonate precursor. Since the aromatic diol compound and the carbonate precursor have hydrophobicity, they can be included in the organic solvent layer among water and the organic solvent, and various water-soluble impurities can be included in the water layer. Accordingly, the main product, the aromatic diol compound, and the impurities can be easily separated with just a simple process of changing the pH.

[0090] In the step of adding acid so that the pH of the above depolymerization reaction product becomes 2 to 8, a step of adding water may be further included. Through this, in the impurity removal step described below, a layer can be formed that is divided into a water layer containing impurities and an organic solvent layer containing an aromatic diol compound and a carbonate precursor.

[0091] The order of the process of adding acid and the process of adding water is not particularly limited, and either adding acid followed by adding water, or adding acid followed by adding water, or adding both water and acid simultaneously is possible.

[0092] Meanwhile, the step of recovering the aromatic diol compound obtained through the depolymerization reaction may include a step of removing impurities after the addition of the acid. The impurities may be hydrophilic substances, such as salt compounds, ionic compounds, acid compounds, etc.

[0093] As described above, after the step of adding acid so that the pH of the depolymerization product becomes 2 to 8, by performing the step of removing impurities from the depolymerization product after the addition of the acid, the depolymerization product forms layers divided into a water layer containing impurities and an organic solvent layer containing an aromatic diol compound and a carbonate precursor, from which the water layer containing impurities can be separated and removed.

[0094] After the acid addition, in the step of removing impurities from the depolymerization product, the aqueous layer can be separated from the organic layer, thereby removing impurities contained in the aqueous layer. The specific separation conditions for separating the aqueous layer from the organic layer are not particularly limited, and various existing purification technologies can be applied without limitation to the specific separation equipment and method. However, as an example, a drain device can be used.

[0095] Meanwhile, the step of recovering the aromatic diol compound obtained in the depolymerization reaction may include a step of separating a carbonate precursor from the depolymerization reaction product. Accordingly, the separated carbonate precursor may include diethyl carbonate.

[0096] In the step of separating the carbonate precursor from the above-mentioned depolymerization product, a step of distilling the depolymerization product under reduced pressure may be included. The examples of the conditions for distilling under reduced pressure are not particularly limited, but as a specific example, the polycarbonate resin may be pressurized under the conditions of a pressure of 200 to 300 mbar and a temperature of 20 to 30°C, and then distilled at low temperature under the conditions of a pressure of 10 to 50 mbar and a temperature of 20 to 30°C.

[0097] The separated carbonate precursor can be recycled without a separate separation and purification process, or, if necessary, through conventional separation and purification processes such as extraction, adsorption, and drying. Specific purification conditions are not significantly limited, and various existing purification technologies can be applied without limitation to specific purification equipment and methods.

[0098] Meanwhile, the step of recovering the aromatic diol compound obtained in the depolymerization reaction may further include a step of purifying the depolymerization reaction product from which the carbonate precursor is separated, after the step of separating the carbonate precursor from the depolymerization reaction product.

[0099] Specifically, the purification step of the depolymerization product from which the carbonate precursor is separated may include a washing step of the depolymerization product from which the carbonate precursor is separated. In addition, the purification step of the depolymerization product from which the carbonate precursor is separated may include an adsorption purification step of the depolymerization product from which the carbonate precursor is separated. In addition, the purification step of the depolymerization product from which the carbonate precursor is separated may include a recrystallization step of the depolymerization product from which the carbonate precursor is separated.

[0100] The order of the washing step; the adsorption purification step; or the recrystallization step; is not particularly limited and may be carried out in any order. However, for example, the washing step; the adsorption purification step; and the recrystallization step may be carried out in this order. The washing step; the adsorption purification step; and the recrystallization step may each be repeated at least once. Various purification technologies known in the art can be applied without limitation to specific washing, adsorption, and recrystallization equipment and methods.

[0101] In the washing step of the depolymerization product from which the carbonate precursor is separated, the depolymerization product from which the carbonate precursor is separated may contain an aromatic diol compound. However, since various impurities remain during the recovery process for obtaining the aromatic diol compound, washing may be performed to sufficiently remove these impurities and secure a high-purity aromatic diol compound.

[0102] Specifically, the washing step may include a step of washing with a solvent at a temperature of 10°C or higher and 30°C or lower, or 20°C or higher and 30°C or lower. The temperature condition refers to the temperature inside the washing container where washing with the solvent is performed, and various heating devices may be applied without limitation to maintain a high temperature exceeding room temperature.

[0103] The solvent used in the above washing step may include one of water, alcohol, and an organic solvent. The organic solvent may be tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0104] The solvent used in the above washing step may be used in a weight ratio of 1 part by weight or more and 30 parts by weight or less, or 1 part by weight or more and 10 parts by weight or less, based on 1 part by weight of the polycarbonate resin used in the depolymerization reaction.

[0105] More specifically, the solvent in the step of washing with a solvent at a temperature of 10°C or higher and 30°C or lower may be an organic solvent. Preferably, methylene chloride may be used as the organic solvent. In this case, the organic solvent may be used in an amount of 1 part by weight or more and 10 parts by weight or less relative to 1 part by weight of the polycarbonate resin.

[0106] In addition, the step of adsorption purification of the depolymerization product from which the carbonate precursor is separated may include a step of adding an adsorbent to the depolymerization product from which the carbonate precursor is separated, performing adsorption purification, and then removing the adsorbent. In the step of adding an adsorbent to the depolymerization product from which the carbonate precursor is separated, performing adsorption purification, and then removing the adsorbent, the adsorbent may be brought into contact with the depolymerization product.

[0107] Examples of the above adsorbent include activated carbon, charcoal, or a mixture thereof. The activated carbon is a black carbon material with micropores manufactured by subjecting raw materials to a carbonization process at approximately 500°C and an activation process at approximately 900°C. Examples are not particularly limited, but various activated carbons such as plant-based, coal-based, petroleum-based, and waste-based activated carbons can be applied without limitation depending on the type of raw material.

[0108] More specific examples include plant-based activated carbons such as palm, wood, and sawdust. Coal-based activated carbons include lignite, bituminous, and anthracite. Petroleum-based activated carbons include petroleum coke and oil carbon. Waste-based activated carbons include synthetic resin and pulp activated carbon.

[0109] The above adsorbent may include at least one type of activated carbon selected from the group consisting of plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, and waste-based activated carbon. That is, the adsorbent may include plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, waste-based activated carbon, or a mixture of two or more types thereof.

[0110] More specifically, the adsorbent may include at least one type of activated carbon selected from the group consisting of palm activated carbon, lignite activated carbon, anthracite activated carbon, and bituminous carbon activated carbon. That is, the adsorbent may include palm activated carbon, lignite activated carbon, anthracite activated carbon, bituminous carbon activated carbon, or a mixture of two or more types thereof.

[0111] The adsorption purification conditions using the above adsorbent are not particularly limited, and various adsorption purification conditions known in the art can be used without limitation. However, for example, the amount of the adsorbent added can be 40 to 60 wt% relative to the polycarbonate resin, the adsorption time can be 1 to 5 hours, and the adsorption method can be stirred adsorption or a lab-type adsorption tower.

[0112] If necessary, a step of adding a solvent to the depolymerization product from which the carbonate precursor is separated before the step of removing the adsorbent after adding an adsorbent to the depolymerization product from which the carbonate precursor is separated and then performing adsorption purification may be further included. An example of the solvent is ethanol, and the ethanol may be added in a ratio of 1 to 20 moles, or 10 to 20 moles, or 15 to 20 moles per mole of the polycarbonate resin. Through the step of adding a solvent to the depolymerization product from which the carbonate precursor is separated, the aromatic diol compound crystals included in the depolymerization product from which the carbonate precursor is separated may be redissolved in the solvent.

[0113] Meanwhile, in the recrystallization step of the depolymerization product from which the carbonate precursor is separated, various impurities contained in the depolymerization product from which the carbonate precursor is separated can be sufficiently removed to secure a high-purity aromatic diol compound.

[0114] Specifically, the recrystallization step may include a step of recrystallizing by adding water to the depolymerization product from which the carbonate precursor is separated. Through the process of recrystallizing by adding water to the depolymerization product from which the carbonate precursor is separated, the solubility of the aromatic diol compound, or its salt, contained in the depolymerization product increases, so that impurities present in the crystals or between the crystals can be dissolved with the solvent as much as possible, and since the dissolved aromatic diol compound has poor solubility compared to the impurities, when the temperature is lowered thereafter, the difference in solubility allows the aromatic diol compound to be easily precipitated as crystals.

[0115] More specifically, in the step of recrystallizing by adding water to the depolymerization product from which the carbonate precursor is separated, 200 to 400 moles, or 250 to 350 moles, of water may be used per 1 mole of the polycarbonate resin. If too little water is used, the temperature for dissolving the aromatic diol compound contained in the depolymerization product from which the carbonate precursor is separated becomes too high, which lowers the process efficiency and makes it difficult to remove impurities through recrystallization. On the other hand, if too much water is used, the solubility of the aromatic diol compound contained in the depolymerization product from which the carbonate precursor is separated becomes too high, which reduces the yield of the aromatic diol compound recovered after recrystallization, and the process efficiency may decrease due to the use of a large amount of solvent.

[0116] If necessary, after the carbonate precursor has undergone a recrystallization step of the separated depolymerization product, an additional process of removing remaining impurities through filtration or adsorption may be performed.

[0117] In addition, if necessary, a drying step may be further included after the recrystallization step. The drying step can remove any remaining solvent, and although the specific drying conditions are not particularly limited, drying may be performed at a temperature of, for example, 10°C to 100°C, or 10°C to 50°C. Various known drying technologies can be applied without limitation to the specific drying equipment and method used during the drying step.

[0118]

[0119] 2. Monomer manufacturing device for recycled plastic synthesis

[0120] According to another embodiment of the invention, an apparatus for producing a monomer composition for synthesizing recycled plastic may be provided, comprising: a reactor for depolymerizing a polycarbonate resin in the presence of alcohol; an inline analyzer inserted into the reactor for monitoring a Raman spectrum of an aromatic diol compound obtained in the depolymerization reaction or alcohol; and a recovery unit for recovering the aromatic diol compound obtained in the depolymerization reaction.

[0121] The content of depolymerizing a polycarbonate resin under the above alcohol includes all of the above-described embodiments. The specific shape, material, and size of the reactor are not particularly limited, and various reactors widely used in conventional polymer depolymerization reactions can be applied without limitation.

[0122] The content of monitoring the Raman spectrum by the aromatic diol compound or alcohol obtained in the depolymerization reaction by inserting it into the above reactor includes all of the above-described embodiments.

[0123] The above-described inline analyzer may include a Raman analyzer. The Raman analyzer may be manufactured to withstand the reaction pressure and inserted into a reactor in which a depolymerization reaction is taking place, thereby collecting reaction information in real time. One end of the Raman analyzer may be in contact with the depolymerization reaction reactants, and the other end may be connected to a computer, thereby enabling real-time analysis of the acquired Raman spectrum. Specifically, the values ​​of Equations 1, 2, and 3 of the above-described embodiment may be analyzed via the computer.

[0124] The inline analyzer may include a detector that contacts the reactants within the reactor. Furthermore, the inline analyzer may further include a computer that analyzes the Raman spectrum measured by the inline analyzer. One end of the inline analyzer contacts the reactants within the reactor, and the other end is connected to the computer, enabling real-time analysis of the acquired spectrum.

[0125] The recovery of the aromatic diol compound obtained through the depolymerization reaction in the above recovery unit includes all of the above-described embodiments. The specific shape, material, and size of the recovery unit are not particularly limited, and various recovery equipment widely used in the conventional depolymerization reaction of polycarbonate can be applied without limitation. However, for example, distillation equipment, washing equipment, filtration equipment, recrystallization equipment, etc. can be used in the recovery unit.

[0126] Although a specific example of a manufacturing device for a monomer composition for synthesizing recycled plastic according to another embodiment of the invention is not particularly limited, an example will be described with reference to FIG. 3 below. The device may include: a reactor (1) for depolymerizing a polycarbonate resin in the presence of alcohol; an inline analyzer (2) inserted into the reactor to monitor a Raman spectrum of an aromatic diol compound or alcohol obtained in the depolymerization reaction; and a recovery unit (5) for recovering the aromatic diol compound obtained in the depolymerization reaction. More specifically, the inline analyzer may include a detection unit (3) in contact with a reactant in the reactor. In addition, the device may further include a computer (4) for analyzing a Raman spectrum measured by the inline analyzer.

[0127]

[0128] 3. Monomer composition for synthesizing recycled plastics

[0129] According to another embodiment of the invention, a monomer composition for synthesizing recycled plastics can be provided, which comprises an aromatic diol compound obtained by the method for producing a monomer composition for synthesizing recycled plastics of the above embodiment, or by the apparatus for producing a monomer composition for synthesizing recycled plastics of the above other embodiment.

[0130] That is, the monomer composition for synthesizing recycled plastic of the other embodiment may be obtained by the method for producing the monomer composition for synthesizing recycled plastic of the one embodiment. The content of the method for producing the monomer composition for synthesizing recycled plastic of the one embodiment includes all of the content described above in the one embodiment.

[0131] In addition, the monomer composition for synthesizing recycled plastics of the other embodiment may be obtained by the apparatus for producing the monomer composition for synthesizing recycled plastics of the other embodiment. The contents of the apparatus for producing the monomer composition for synthesizing recycled plastics of the other embodiment include all of the contents described above in the other embodiment.

[0132] Specific examples of the above aromatic diol compounds include bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, Examples thereof include 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, or a mixture of two or more thereof. Preferably, the aromatic diol compound of the monomer composition for synthesizing recycled plastic of the above embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0133] The aromatic diol compound is characterized in that it is obtained from the method for producing a monomer composition for synthesizing recycled plastics according to the above embodiment, or from the apparatus for producing a monomer composition for synthesizing recycled plastics according to the other embodiment. That is, the aromatic diol compound is characterized in that it is recovered from the polycarbonate resin used for recovering the monomer composition for synthesizing recycled plastics. Therefore, in order to produce the monomer composition for synthesizing recycled plastics according to the other embodiment, a case in which a new aromatic diol compound is added externally separately from recovery from the polycarbonate resin is not included in the category of the aromatic diol compound of the present invention.

[0134] Specifically, "recovered from the polycarbonate resin" means obtained through a depolymerization reaction of the polycarbonate resin. The depolymerization reaction can be performed under acidic, neutral, or alkaline conditions, and in particular, the depolymerization reaction can proceed under alkaline (alkaline) conditions. In particular, the depolymerization reaction is preferably performed in an ethanol solvent, as described below.

[0135]

[0136] 4. Recycled plastic

[0137] According to another embodiment of the invention, a recycled plastic comprising a reaction product of a monomer composition for synthesizing recycled plastic and a comonomer of the other embodiment can be provided.

[0138] The content of the monomer composition for synthesizing recycled plastic of the above other embodiments includes all of the content described above in the above other embodiments.

[0139] Examples corresponding to the above recycled plastics are not particularly limited, and various plastics synthesized using aromatic diol compounds such as bisphenol A and carbonate precursors such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate as monomers can be applied without limitation, and a more specific example is polycarbonate resin.

[0140] The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization or copolymerization reaction of a monomer including an aromatic diol compound and a carbonate precursor. When one carbonate repeating unit is contained using only one aromatic diol compound and one carbonate precursor, a homopolymer can be synthesized. In addition, a copolymer can be synthesized when two or more carbonates are contained by using one aromatic diol compound and two or more carbonate precursors as the monomer, or using two or more aromatic diol compounds and one carbonate precursor, or using one or more other diols in addition to one aromatic diol compound and one carbonate precursor. The homopolymer or copolymer can include all low molecular weight compounds, oligomers, and polymers according to the molecular weight range.

[0141] More specifically, in the recycled plastic comprising the monomer composition for synthesizing the recycled plastic of the above embodiment and the reaction product of the comonomer, a carbonate precursor may be used as the comonomer. Specific examples of the carbonate precursor include phosgene, triphosgene, diphosgene, bromophosgene, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, or bishaloformate.

[0142] Examples of the reaction process of the monomer composition and comonomer for synthesizing the above polycarbonate resin for synthesizing recycled plastic are not particularly limited, and various polycarbonate manufacturing methods known in the art can be applied without limitation.

[0143] However, as an example of the above polycarbonate manufacturing method, a polycarbonate manufacturing method including a step of polymerizing a composition including a monomer composition for synthesizing recycled plastic and a comonomer may be used. In this case, the polymerization may be performed through interfacial polymerization, and during interfacial polymerization, the polymerization reaction can be performed at normal pressure and low temperature, and molecular weight control is easy.

[0144] The polymerization temperature may be 0°C to 40°C, and the reaction time may be 10 minutes to 5 hours. In addition, the pH during the reaction may be maintained at 9 or higher or 11 or higher.

[0145] The solvent that can be used for the above polymerization is not particularly limited as long as it is a solvent used in the polymerization of polycarbonate in the art, and for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene can be used.

[0146] In addition, the polymerization can be carried out in the presence of an acid binder, and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine can be used as the acid binder.

[0147] In addition, in order to control the molecular weight of the polycarbonate during the polymerization, polymerization can be performed in the presence of a molecular weight regulator. The molecular weight regulator can be an alkylphenol having 1 to 20 carbon atoms, and specific examples thereof include p-tert-butylphenol, p-cumylphenol, decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, or triacontylphenol. The molecular weight regulator can be added before the start of polymerization, during the start of polymerization, or after the start of polymerization. The molecular weight regulator can be used in an amount of 0.01 to 10 parts by weight, or 0.1 to 6 parts by weight, based on 100 parts by weight of the aromatic diol compound, and a desired molecular weight can be obtained within this range.

[0148] In addition, in order to promote the polymerization reaction, a reaction promoter such as a tertiary amine compound, a quaternary ammonium compound, a quaternary phosphonium compound, etc., such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, can be additionally used.

[0149]

[0150] 5. Molded products

[0151] According to another embodiment of the invention, a molded article comprising the recycled plastic of the other embodiment may be provided. The content of the recycled plastic includes all of the content described above in the other embodiment.

[0152] The above molded product may be obtained by applying various known plastic molding methods to the above recycled plastic without limitation, and examples of the molding methods include injection molding, foam injection molding, blow molding, or extrusion molding.

[0153] The above examples of molded products are not particularly limited and can be applied to a variety of molded products using plastics without limitation. Examples of molded products include automotive parts, electrical and electronic products, communication products, household goods, building materials, optical components, and exterior materials.

[0154] In addition to the recycled plastic of the other embodiments, the above-mentioned molded product may additionally include one or more additives selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent whitening agents, ultraviolet absorbers, pigments, and dyes, as needed.

[0155] As an example of a method for manufacturing the above-mentioned molded product, the method may include a step of mixing the recycled plastic and additives of the other embodiment well using a mixer, extruding them with an extruder to manufacture pellets, drying the pellets, and then injecting them with an injection molding machine.

[0156] According to the present invention, a method for producing a monomer composition for synthesizing recycled plastic, which improves efficiency by optimizing reaction conditions through real-time monitoring of a process for recycling an aromatic diol compound by chemical decomposition of a polycarbonate resin, an apparatus for producing a monomer composition for synthesizing recycled plastic, and a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded article using the same can be provided.

[0157] Figure 1 shows the Raman spectrum obtained in the example.

[0158] Figure 2 shows the integral ratio of aromatic diol compounds and the integral ratio of alcohol obtained in Example 1.

[0159] Figure 3 is a schematic diagram of a manufacturing device for a monomer composition for synthesizing recycled plastic.

[0160] The invention is described in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited by the following examples.

[0161]

[0162] <Example: Preparation of recycled bisphenol A monomer composition>

[0163] Example 1

[0164] (1. Decomposition step) 1 mol of waste polycarbonate (PC) was introduced into the reactor (1) and dissolved using methylene chloride (MC), and then foreign substances were filtered out. Afterwards, 11 mol of ethanol (EtOH), 0.2 mol of sodium hydroxide (NaOH), and an antioxidant were introduced and stirred at 60°C to carry out the PC depolymerization reaction.

[0165] During the above PC depolymerization reaction, the Raman probe, which is an in-line analyzer (2), was inserted into the reactor (1), and the detection unit (3) was not disturbed due to the viscosity of polycarbonate (PC) during stirring. After the start of the reaction, the Raman spectrum measured at regular time intervals (approximately 3 minutes) for a total of 6 hours was analyzed in real time using a computer (4) program, and the reaction was terminated at the reaction optimum point (BPA / MC Raman integration ratio = 0.12).

[0166] (2. pH adjustment) The product of the above depolymerization reaction was cooled to 30°C or lower, and then 10% hydrochloric acid (HCl) and water were added to adjust the pH to 8.

[0167] (3. Layer separation) After the water layer and the methylene chloride (MC) layer were formed, the organic layer located at the bottom was recovered using the drain device at the bottom of the reactor, and the water layer located at the top was discharged and discarded.

[0168] (4. Distillation) Afterwards, the recovered methylene chloride (MC) layer was moved to the recovery unit (5) and subjected to low-temperature distillation by reducing the pressure from 250 mbar, 20 to 30°C to 30 mbar, 30°C, to classify and recover the by-product diethyl carbonate (DEC).

[0169] (5. Purification step - filtration) Afterwards, the residue from which diethyl carbonate (DEC) was removed was washed at 20 to 30°C using methylene chloride (MC) twice the mass of PC used, and vacuum filtered.

[0170] (6-1. Additional purification step - re-dissolution step) After that, bisphenol A was added to 16.6 mol of ethanol and re-dissolved.

[0171] (6-2. Additional purification step - adsorption step) Afterwards, brown activated carbon was added as an adsorbent at a ratio of 30 wt% relative to waste polycarbonate, purified through an adsorption tower for 3 hours, and then the brown activated carbon was removed through filtration.

[0172] (6-3. Additional purification step - recrystallization step) After that, water was added and bisphenol A was recrystallized, and the obtained slurry was vacuum filtered at 20 to 30°C to recover bisphenol A (BPA) crystals.

[0173] (7. Drying step) Afterwards, a recycled bisphenol A monomer composition was manufactured by recovering recycled bisphenol A (BPA) by vacuum drying in a 40 ℃ convection oven.

[0174]

[0175] Example 2

[0176] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (1. Decomposition step) of Example 1 was changed as follows.

[0177] (1. Decomposition step) 1 mol of waste polycarbonate (PC) was added to the reactor (1) and dissolved using methylene chloride (MC), and then foreign substances were filtered out. Afterwards, 11 mol of ethanol (EtOH), 0.2 mol of sodium hydroxide (NaOH), and an antioxidant were added and stirred at 80°C to carry out the PC depolymerization reaction.

[0178] During the above PC depolymerization reaction, the Raman probe, which is an in-line analyzer (2), was inserted into the reactor (1), and the detection unit (3) was not disturbed due to the viscosity of polycarbonate (PC) during stirring. After the start of the reaction, the Raman spectrum measured at regular time intervals (approximately 3 minutes) for a total of 6 hours was analyzed in real time by a computer (4), and the reaction was terminated at the reaction optimum point (BPA / MC Raman integration ratio = 0.12).

[0179]

[0180] <Experimental Example>

[0181] The physical properties were measured using the following method, and the results are shown in Tables 1 and 2 and Figures 1 and 2.

[0182]

[0183] 1. Raman spectrum analysis results

[0184] (1) Aromatic diol compound integration ratio

[0185] In the above example (1. Decomposition step), the integral ratio of bisphenol A (BPA), an aromatic diol compound, was obtained through an in-line Raman analysis device at regular time intervals (about 3 minutes) for a total of 6 hours after the start of the PC depolymerization reaction, and is shown in Table 1 and Figure 2 for Example 1, and Table 2 for Example 2. Specifically, the integral ratio of the aromatic diol compound (BPA) is as shown in the following mathematical formula 1, BPA band (791.2 cm -1 861.5 cm inland -1 ) The integral value is MC band (663.4 cm -1785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 ) can be obtained by dividing by the integral value.

[0186] [Mathematical Formula 1]

[0187] Aromatic diol compound integral ratio = {791.2 cm on Raman spectrum -1 861.5 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)}

[0188] In the above mathematical formula 1, 791.2 cm on the Raman spectrum -1 861.5 cm inland -1 The region is a spectrum due to bisphenol A (BPA), and is 663.4 cm in the Raman spectrum. -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is a spectrum by methylene chloride (MC).

[0189] The above Raman analysis was performed using MarqMetrix's All-in-one equipment and BallProbe to measure the spectrum inside the reactor in real time under excitation laser (785 nm, 400 Mw) conditions, and the regions of each component of MC and BPA were linearly baseline corrected.

[0190] (2) Alcohol concentration ratio

[0191] In the above example (1. Decomposition step), the integrated ratio of ethanol (EtOH), which is alcohol, was obtained through an in-line Raman analysis device at regular time intervals (about 3 minutes) for a total of 6 hours after the start of the PC depolymerization reaction, and is shown in Table 1 and Figure 2 for Example 1. Specifically, the integrated ratio of alcohol (EtOH) is as shown in the following mathematical formula 2, EtOH band (849.7 cm -1 910 cm inland -1 ) The integral value is MC band (663.4 cm -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 ) can be obtained by dividing by the integral value.

[0192] [Mathematical Formula 2]

[0193] Alcohol integral ratio = {849.7 cm on Raman spectrum -1 910 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)}

[0194] In the above mathematical equation 2, 849.7 cm on the Raman spectrum -1 910 cm inland -1 The region is a spectrum by ethanol (EtOH), and is 663.4 cm in the Raman spectrum. -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is a spectrum by methylene chloride (MC).

[0195] The above Raman analysis was performed using MarqMetrix All-in-one equipment and BallProbe to measure the spectrum inside the reactor in real time under excitation laser (785 nm, 400 Mw) conditions, and the regions of each component, EtOH and BPA, were linearly baseline corrected.

[0196]

[0197] 2. BPA yield

[0198] In the above example (1. Decomposition step), the weight of bisphenol A (BPA) produced by the depolymerization reaction for a total of 6 hours was confirmed through HPLC measurement at regular time intervals (approximately 3 minutes) after the start of the PC depolymerization reaction, and the weight of BPA produced when the polycarbonate used in the reaction was 100% decomposed was measured, thereby calculating the yield of BPA as in Equation 4 below.

[0199] [Formula 4]

[0200] Yield (%) = (W1 / W0) * 100

[0201] In the above equation 4, W0 is the mass of BPA obtained upon 100% decomposition, and W1 is the mass of BPA actually obtained. Specifically, when about 100 g of polycarbonate is decomposed, the mass of BPA theoretically obtained upon 100% decomposition is 89 g. If the mass of BPA actually obtained is 80 g, the yield is (80 / 89) * 100 = 90%.

[0202]

[0203] Experimental example measurement results for Example 1 Measurement time (minutes) Mathematical formula 1 Mathematical formula 2 BPA yield (%) 30.05 0.18 9.86 0.08 20.17 9 16.8 16 0.10 10.17 30.9 25 0.10 5 0.11 5 5.8 36 0.10 6 0.10 5 6 6.25 5 0.11 10.10 7 8.37 00.11 20.09 8 2.18 00.11 3 0.09 7 8 3.6 1 20 0.12 0.09 5 9 0.1

[0204] Experimental example for Example 2 Measurement results Measurement time (minutes) Mathematical formula 1 BPA yield (%) 30.06 9.36 0.09 17.116 0.105 31.125 0.116 5.46 00.115 88.1700.116 89.98 00.118 90.1900.129 0.210 00.122 9 2.1

Claims

1. A step of depolymerizing a polycarbonate resin in alcohol; A step of monitoring the Raman spectrum of an aromatic diol compound or alcohol obtained from the depolymerization reaction in a reactor in which the depolymerization reaction is carried out; and A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of recovering the above aromatic diol compound.

2. In paragraph 1, The step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out is as follows. A method for producing a monomer composition for synthesizing recycled plastic, the method comprising: performing a Raman measurement using a Raman meter inserted into a reactor.

3. In paragraph 1, The step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out is as follows. A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of measuring an integral ratio of an aromatic diol compound according to the following mathematical formula 1: [Mathematical Formula 1] Aromatic diol compound integral ratio = {791.2 cm on Raman spectrum -1 861.5 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)} In the above mathematical formula 1, 791.2 cm on the Raman spectrum -1 861.5 cm inland -1 The region is a spectrum due to aromatic diol compounds, Raman spectrum at 663.4 cm -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is the spectrum due to the reaction solvent.

4. In paragraph 3, A method for producing a monomer composition for synthesizing recycled plastic, wherein the depolymerization reaction is terminated when the aromatic diol compound integration ratio according to the above mathematical formula 1 is 0.115 to 0.

125.

5. In paragraph 1, The step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out is as follows. A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of measuring an alcohol integration ratio according to the following mathematical formula 2: [Mathematical Formula 2] Alcohol integral ratio = {849.7 cm on Raman spectrum -1 910 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)} In the above mathematical equation 2, 849.7 cm on the Raman spectrum -1 910 cm inland -1 The area is the spectrum by alcohol, Raman spectrum at 663.4 cm -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is the spectrum due to the reaction solvent.

6. In paragraph 5, A method for producing a monomer composition for synthesizing recycled plastic, wherein the depolymerization reaction is terminated when the alcohol integration ratio according to the above mathematical formula 2 is 0.09 to 0.

1.

7. In paragraph 1, A method for producing a monomer composition for synthesizing recycled plastic, wherein the aromatic diol compound is bisphenol A.

8. In paragraph 1, A method for producing a monomer composition for synthesizing recycled plastic, wherein the alcohol is ethanol.

9. In paragraph 1, The step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out is as follows. A method for producing a monomer composition for synthesizing recycled plastic, further comprising a step of monitoring a Raman spectrum due to impurities derived from aromatic diol compounds generated by the above depolymerization reaction.

10. In paragraph 9, The step of monitoring the Raman spectrum due to impurities derived from aromatic diol compounds generated by the above depolymerization reaction is as follows: A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of measuring the integral ratio of impurities derived from aromatic diol compounds according to the following mathematical formula 3: [Mathematical Formula 3] The integral ratio of impurities derived from aromatic diol compounds = {800 cm on the Raman spectrum -1 850 cm inland -1 Integral value of the region / (663.4 cm on the Raman spectrum) -1 785.1 cm inland -1 Integral value of the region + Raman spectrum at 234.8 cm -1 337.1 cm inland -1 (integral of the domain)} In the above mathematical formula 3, 800 cm on the Raman spectrum -1 850 cm inland -1 The region is a spectrum due to impurities derived from aromatic diol compounds, Raman spectrum at 663.4 cm -1 785.1 cm inland -1 , and 234.8 cm -1 337.1 cm inland -1 The region is the spectrum due to the reaction solvent.

11. In paragraph 10, A method for producing a monomer composition for synthesizing recycled plastic, wherein the depolymerization reaction is terminated when the integral ratio of impurities derived from aromatic diol compounds according to the above mathematical formula 3 exceeds 0.

12.

12. In paragraph 1, The step of monitoring the Raman spectrum of the aromatic diol compound or alcohol obtained from the depolymerization reaction in the reactor in which the depolymerization reaction is carried out is as follows. A method for producing a monomer composition for synthesizing recycled plastic, wherein the process is repeated at intervals of 5 minutes or less.

13. A reactor for depolymerizing polycarbonate resin in alcohol; An inline analyzer inserted into the reactor to monitor the Raman spectrum of the aromatic diol compound or alcohol obtained in the depolymerization reaction; and A device for manufacturing a monomer composition for synthesizing recycled plastic, comprising a recovery unit for recovering an aromatic diol compound obtained in the above depolymerization reaction.

14. In paragraph 13, The above inline analyzer A device for manufacturing a monomer composition for synthesizing recycled plastic, comprising a Raman measuring device.

15. In paragraph 13, A device for manufacturing a monomer composition for synthesizing recycled plastic, further comprising a computer for analyzing a Raman spectrum measured by the above inline analyzer.

16. In paragraph 13, The above inline analyzer is a device for manufacturing a monomer composition for synthesizing recycled plastic, including a detection unit in contact with a reactant in a reactor.

17. A monomer composition for synthesizing recycled plastic, comprising an aromatic diol compound obtained by the method for producing a monomer composition for synthesizing recycled plastic of paragraph 1 or the apparatus for producing a monomer composition for synthesizing recycled plastic of paragraph 13.

18. A recycled plastic comprising a monomer composition for synthesizing recycled plastic and a reaction product of a comonomer of Article 17.

19. A molded product containing recycled plastic of Article 18.

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